• Title/Summary/Keyword: Al alloys

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Study on Grain Refinement of Al-7Si Based Alloys with TiC (Al-7Si 합급의 결정립 미세화에 미치는 TiC 첨가의 영향)

  • Han, Yun-Sung;Choi, Chang-Ock
    • Journal of Korea Foundry Society
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    • v.23 no.2
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    • pp.63-68
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    • 2003
  • Al-Ti-C grain refiner form a relatively new alternative to the existing class of Al-Ti-B type grain refiners for achieving fine equiaxed structures in aluminum alloys during casting and solidification. The present study was carried out to investigate the influence of Al-Ti-C master alloys on the grain structure of Al-7Si alloys. The present study also investigates the relationship between grain refining efficiency and concentrations of Fe and Si in hypo-eutectic Al-Si alloys using Al-3Ti-0.13C master alloys. It is found that several parameters affect significantly the grain refining performance in silumin alloys. The present study reports the influence of various parameters such as alloy content, master alloy addition level, melt holding time and superheat on the grain refining efficiency in Al-7Si alloys.

Effects of Zn and Mg Amounts on the Properties of High Thermal Conductivity Al-Zn-Mg-Fe Alloys for Die Casting (다이캐스팅용 고열전도도 Al-Zn-Mg-Fe 합금의 특성에 미치는 Zn 및 Mg 첨가량의 영향)

  • Kim, Ki-Tae;Lim, Young-Suk;Shin, Je-Sik;Ko, Se-Hyun;Kim, Jeong-Min
    • Journal of Korea Foundry Society
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    • v.33 no.3
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    • pp.113-121
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    • 2013
  • The effects of Zn and Mg amounts on the solidification characteristics, microstructure, thermal conductivity and tensile strength of Al-Zn-Mg-Fe alloys were investigated for the development of high thermal conductivity aluminium alloys for die casting. Zn and Mg amounts in Al-Zn-Mg-Fe alloys had a little effect on the liquidus / solidus temperature, the latent heat for solidification and the fluidity of Al-Zn-Mg-Fe alloys. Thermo-physical modelling of Al-Zn-Mg-Fe alloys by JMatPro program showed $MgZn_2$, AlCuMgZn and Al3Fe phases on microstructure of their alloys. Increase of Zn and Mg amounts in Al-Zn-Mg-Fe alloys resulted in gradual reduction of the thermal conductivity of their alloys. Increase of Mg amounts in Al-2%Zn-Mg-Fe alloys had little effect on the tensile strength of their alloys, but increase of Mg amounts in Al-4%Zn-Mg-Fe alloys resulted in steep increase of the tensile strength of their alloys.

Evaluation of Metal-mold Reactions and Fluidity of TiAl Alloys (TiAl 합금의 주형계면반응 및 유동성 평가)

  • Lee, Sang-Hwa;Sung, Si-Young;Choi, Bong-Jae;Kim, Myoung-Gyun;Kim, Young-Jig
    • Journal of Korea Foundry Society
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    • v.26 no.2
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    • pp.98-103
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    • 2006
  • Metal-mold reactions between investment mold and TiAl alloys were investigated for the economic net-shape forming of TiAl alloys. The effect of mold preheating temperatures on the metal-mold reaction were investigated using a vacuum induction-melting furnace. In the case of TiAl alloys, there were no ${\alpha}$-case formation reactions. There were neither interstitial nor substitutional ${\alpha}$-case formations as TiAl alloys have both negligible solubility of oxygen and low activity in molten states. The fluidity of TiAl alloys increases with mold preheating temperature since they have a peritectic reaction that appears in the form of envelope, surrounding each particles of the primary constituent. The results of the investment casting of TiAl alloys confirm that the casting route in our study can be an effective approach for the economic net-shape forming of TiAl alloys.

Effects of Alloying Elements on the Properties of High Strength and High Thermal Conductivity Al-Zn-Mg-Fe Alloy for Die Casting (다이캐스팅용 Al-Zn-Mg-Fe 합금의 특성에 미치는 Zn 및 Mg 첨가의 영향)

  • Kim, Ki-Tae;Lim, Young-Suk;Shin, Je-Sik;Ko, Se-Hyun;Kim, Jeong-Min
    • Journal of Korea Foundry Society
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    • v.33 no.4
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    • pp.171-180
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    • 2013
  • The effects of alloying elements on the solidification characteristics, microstructure, thermal conductivity, and tensile strength of Al-Zn-Mg-Fe alloys were investigated for the development of high strength and high thermal conductivity aluminium alloy for die casting. The amounts of Zn and Mg in Al-Zn-Mg-Fe alloys had little effect on the liquidus/solidus temperature, the latent heat for solidification, the energy release for solidification and the fluidity of Al-Zn-Mg-Fe alloys. Thermo-physical modelling of Al-Zn-Mg-Fe alloys by the JMatPro program showed $MgZn_2$, AlCuMgZn and $Al_3Fe$ phases in the microstructure of the alloys. Increased amounts of Mg in Al-Zn-Mg-Fe alloys resulted in phase transformation, such as $MgZn_2{\Rightarrow}MgZn_2+AlCuMgZn{\Rightarrow}AlCuMgZn$ in the microstructure of the alloys. Increased amounts of Zn and Mg in Al-Zn-Mg-Fe alloys resulted in a gradual reduction of the thermal conductivity of the alloys. Increased amounts of Zn and Mg in Al-Zn-Mg-Fe alloys had little effect on the tensile strength of the alloys.

Cavitation Characteristics of Al-Mg and Al-Mg-Si Alloy for Ship in Sea Water (선체 재료용 Al-Mg 합금과 Al-Mg-Si 합금의 해수 내 캐비테이션 특성)

  • Kim, Seong-Jong;Kim, Kyu-Hwan;Lee, Seung-Jun
    • Corrosion Science and Technology
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    • v.10 no.4
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    • pp.136-142
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    • 2011
  • Al alloys have been used widely for commercial and military ships in most ocean countries since mid-1950s, and the value as light metal with high mechanical strength has been proven. As the safety and fuel efficiency of Al ships have improved, she can carry more freight, sail faster and travel longer distances. Furthermore, in the shipbuilding industry, Al alloys are applied as structural materials for ships to various areas including the deck of luxurious cruises, battleships and leisure ships. In addition, Al alloys are being spotlighted as environmental-friendly material as they can be recycled even after end of lifespan. However, Al alloys for ships must be carefully selected after considering corrosion resistance, endurance, strength, and weldability in sea water environment. Al alloys to satisfy these conditions are used widely include 5000 series Al-Mg alloy and 6000 series Al-Mg-Si alloy. Thus, this study selected and evaluated the cavitation characteristics of the 5000 series Al alloys that are used in hulls that directly contact seawater and the 6000 Al alloys that are used in the upper structures of ships. Results of cavitation test with time, weightloss and cavitation rate of 5456-H116 showed the smallest damage among 5052-O, 5456-H116 and 6061-T6.

Wear properties of Al-Pb alloys produced by a forced stirring method (강제교반법으로 제조된 Al-Pb계 베어링 합금의 마모특성)

  • 임화영;허무영;임대순
    • Tribology and Lubricants
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    • v.8 no.1
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    • pp.70-77
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    • 1992
  • Al-Pb-Si bearing alloys were produced by a forced stirring method and a rapid solidification process to study wear properties of bearing alloys. A homogeneous distribution of Pb particles in Al matrix could be obtained by means of the forced stirring and the rapid cooling during the casting. The wear properties of bearing alloys were tested by a pin-on-disc wear tester. The change in microstructure according to the alloy manufacturing variables was observed by the backscattered electron images. Al-Pb and Al-Si binary alloys showed a transition from mild to severe wear. The transition was not found in Al-Pb-Si ternary alloys. It could be concluded that the lubricatioin effect of Pb and the strengthening effect of Si in the ternary alloys enhanced the bearing properties. A Al-25%Pb-13%Si alloy showed the lowest coefficient of friction in this experiment. It indicated that the optimum concentration of alloy was 25% Pb and 13% Si when the forced stirring of melt and water-cooled-copper-mold solidification were adopted.

Mechanical Properties of Al-Ti Base Alloys Processed Via Rapid Solidification and Mechanical Alloying (급냉응고 및 기계적 합금화된 Al-Ti계 합금의 기계적 성질)

  • 최철진
    • Journal of Powder Materials
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    • v.2 no.1
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    • pp.36-43
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    • 1995
  • Rapidly solidified and mechanically alloyed Al-Ti base alloys were prepared by gas atomization and attritor milling separately. The gas atomized and the mechanically alloyed powders were consolidated after preheating at $450^{\circ}C$, and then heat treated isochronally for 1 hour to observe the microstructures and to investigate the mechanical properties. Stable phases of precipitates in the Al-Ti-Si and the Al-Ti-Zr alloys were identified as DO22-$(Al,Si)_3Ti$ and $Do_{23}-Al_3(Ti, Zr)$ each. Among the alloys, the mechanically alloyed Al-l0Ti-2Si alloy showed superior thermal stability and mechanical properties at elevated temperature. The additions of third elements, such as Si and Zr, to Al-Ti alloys seemed to improve the mechnical properties remarkably by stabilizing the microstructure and the precipitate phases in the consolidated alloys.

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A Study on Stress Corrosion of Al-8ti-1B Alloys by Mechanical Alloying (기계적 합금화한 Al-8Ti-1B 합금의 응력부식에 관한 연구)

  • 김기주;강성군;백영남
    • Journal of the Korean institute of surface engineering
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    • v.27 no.4
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    • pp.215-222
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    • 1994
  • The role dispersoids has been studied in a number of researches as a key point for the high strength application of dispersion strengthened aluminum alloy. The mechanical alloying(MA) process with high mechanical properties of dispersion strengthened MA Al-8Ti-1B alloys were invested in order to evaluate their stress corrosion cracking(SCC) application. SCC properties of the mechanically alloyed Al-8Ti-1B were studied using slow strain rate test(SSRT). In this study Al-8Ti-1B alloy were more susceptible to SCC in solutions of pH=2.01 and 13.2 than pH=6.81 solution. In this study Al-8Ti-1B alloys by MA had more SCC resistance than Al-8Ti alloys or Al 7075-T73 alloys. So Al-8Ti-1B alloys by MA had more resistance in SSRT SCC susceptinility test than any other above alloying metals.

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Effect of Fe on the High Temperature Oxidation of TiAl Alloys (TiAl 합금의 고온 산화에 미치는 Fe의 영향)

  • 김미현;이동복
    • Journal of the Korean institute of surface engineering
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    • v.33 no.4
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    • pp.281-288
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    • 2000
  • To understand the effect of Fe on the oxidation behavior of TiAl alloys, TiAl-(2, 4, 6at% )Fe were oxidized at 800 and 90$0^{\circ}C$ in air. The oxidation resistance of TiAl-Fe alloys increased with increasing an iron content. The scales formed consisted of an outer $TiO_2$ layer, an intermediate $A1_2$$O_3$ layer, and an inner mixed ($TiO_2$+$A1_2$$O_3$) layer, being similar to other common TiAl alloys. But, the scales formed on TiAl-Fe alloys were generally thin compared to those formed on pure TiAl, and contained dissolved iron. Below the oxide scale, an oxygen affected zone was formed. This beneficial effects of Fe on increasing the oxidation resistance and scale adherence of TiAl alloys were attributed to the refinement of oxide grains, increased scale adherence and the enhanced alumina-forming tendency.

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Effect of Al and Mg Contents on Wettability and Reactivity of Molten Zn-Al-Mg Alloys on Steel Sheets Covered with MnO and SiO2 Layers

  • Huh, Joo-Youl;Hwang, Min-Je;Shim, Seung-Woo;Kim, Tae-Chul;Kim, Jong-Sang
    • Metals and materials international
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    • v.24 no.6
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    • pp.1241-1248
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    • 2018
  • The reactive wetting behaviors of molten Zn-Al-Mg alloys on MnO- and amorphous (a-) $SiO_2$-covered steel sheets were investigated by the sessile drop method, as a function of the Al and Mg contents in the alloys. The sessile drop tests were carried out at $460^{\circ}C$ and the variation in the contact angles (${\theta}_c$) of alloys containing 0.2-2.5 wt% Al and 0-3.0 wt% Mg was monitored for 20 s. For all the alloys, the MnO-covered steel substrate exhibited reactive wetting whereas the $a-SiO_2$-covered steel exhibited nonreactive, nonwetting (${\theta}_c>90^{\circ}$) behavior. The MnO layer was rapidly removed by Al and Mg contained in the alloys. The wetting of the MnO-covered steel sheet significantly improved upon increasing the Mg content but decreased upon increasing the Al content, indicating that the surface tension of the alloy droplet is the main factor controlling its wettability. Although the reactions of Al and Mg in molten alloys with the $a-SiO_2$ layer were found to be sluggish, the wettability of Zn-Al-Mg alloys on the $a-SiO_2$ layer improved upon increasing the Al and Mg contents. These results suggest that the wetting of advanced high-strength steel sheets, the surface oxide layer of which consists of a mixture of MnO and $SiO_2$, with Zn-Al-Mg alloys could be most effectively improved by increasing the Mg content of the alloys.